Direct measurement of effects of shallow-trench isolation on carrier profiles in sub-50 nm N-MOSFETs

The effects of shallow-trench isolation (STI) on the carrier profile of the extension region in sub-50-nm n-MOSFET were directly measured for the first time. The extension overlap length drastically decreased by 3 run within a distance from STI (Y) of 50 nm. In contrast, the channel concentration gradually increased within Y of 100 nm. The STI effect was also measured for transistors with a gate width of less than 130 nm in 6T-SRAM cell. Reduction of the STI effect by nitrogen co-implant suppressed sub-threshold leakage current by up to an order of magnitude and decreased fluctuation in the threshold voltage by 8 %.